Image capturing method

1. An image capturing method of capturing an image of a subject while emitting light from two light-emitting sources toward the subject, the light-emitting sources being configured so that color temperatures of light emitted from the respective light-emitting sources are different from each other and a ratio between the volumes of light emitted from the light-emitting sources is variably controllable, the method comprising: a light-source color obtaining step of obtaining a light-source color of ambient light; a preliminary image capturing step including a no-light-emission image capturing step of capturing an image of the subject without light emission from the two light-emitting sources, and a light-emission image capturing step of capturing an image of the subject with light emitted from the two light-emitting sources; a light-emitting source light volume obtaining step of obtaining light volume information indicating a relationship between the light volume related to ambient light and the total volume of light from the two light-emitting sources, on the basis of the images of the subject captured in the preliminary image capturing step; an image capturing step of capturing an image of the subject while emitting light from the two light-emitting sources toward the subject in such a manner that volumes of light emitted from the two light-emitting sources respectively correspond to those represented by a predetermined point which is (i) an intersection point of a first line and a line segment or (ii) a point close to the intersection point in xy chromaticity coordinates, on the basis of the intersection point and the light volume information obtained in the light-emitting source light volume obtaining step, the first line passing through a first coordinate point in the xy chromaticity coordinates which represents the light-source color obtained in the light-source color obtaining step, the first line being drawn so as to cross the line segment at a predetermined angle, the line segment connecting two coordinate points in the xy chromaticity coordinates which points respectively represent colors of light emitted from the respective two light-emitting sources; and a White Balance adjustment step of performing White Balance adjustment on the image captured in the image capturing step on a basis of a White Balance adjustment correction value obtained with reference to a second coordinate point which is on a second line and corresponds to the light volume information obtained in the light-emitting source light volume obtaining step, the second line passing through the predetermined point and the first coordinate point in the xy chromaticity coordinates which represents to the light-source color, wherein when: a color component ratio of R, G, and B signals which are obtained from the image captured in the no-light-emission image capturing step and normalized with respect to G signal is defined as P 0 _ r , P 0 _ g , P 0 _ b ; a color component ratio of a difference between (i) R, G, and B signals obtained from the image captured in the light-emission image capturing step and (ii) R, G, and B signals obtained from the image captured in the no-light-emission image capturing step, values of which differences are normalized with respect to G signal, is defined as P 1 _ r , P 1 _ g , P 1 _ b ; and a color component ratio of R, G, and B components of a mixed color of combined light emitted from the two light-emitting sources normalized with respect to G component is defined as P 2 _ r , P 2 _ g , P 2 _ b , a color component ratio Pe_r, Pe_g, Pe_b of R, G, and B components of the light-source color of ambient light normalized with respect to G component is calculated on the basis of an equation in which: Pe_i=P 0 _ i *P 2 _ i /P 1 _ i , where i designates each of r, q and b: i=r, i=g, and i=b.

2. An image capturing method of capturing an image of a subject while emitting light from two light-emitting sources toward the subject, the light-emitting sources being configured so that color temperatures of light emitted from the respective light-emitting sources are different from each other and a ratio between the volumes of light emitted from the light-emitting sources is variably controllable, the method comprising: a light-source color obtaining step of obtaining a light-source color of ambient light; a preliminary image capturing step including a no-light-emission image capturing step of capturing an image of the subject without light emission from the two light-emitting sources, and a light-emission image capturing step of capturing an image of the subject with light emitted from the two light-emitting sources; a light-emitting source light volume obtaining step of obtaining light volume information indicating a relationship between the light volume related to ambient light and the total volume of light from the two light-emitting sources, on the basis of the images of the subject captured in the preliminary image capturing step; an image capturing step of capturing an image of the subject while emitting light from the two light-emitting sources toward the subject in such a manner that the volumes of light emitted from the two light-emitting sources respectively correspond to those represented by a predetermined point which is (i) an intersection point of a first line and a line segment or (ii) a point close to the intersection point in xy chromaticity coordinates, on the basis of the intersection point and the light volume information obtained in the light-emitting source light volume obtaining step, the first line passing through a first coordinate point in the xy chromaticity coordinates which represents the light-source color obtained in the light-source color obtaining step, the first line being drawn so as to orthogonally cross the line segment, the line segment connecting two coordinate points in the xy chromaticity coordinates which points respectively represent colors of light emitted from the respective two light-emitting sources; and a White Balance adjustment step of performing White Balance adjustment on the image captured in the image capturing step on a basis of a White Balance adjustment correction value obtained with reference to a second coordinate point which is on a second line and corresponds to the light volume information obtained in the light-emitting source light volume obtaining step, the second line passing through the predetermined point and the first coordinate point in the xy chromaticity coordinates which represents to the light-source color.

3. An image capturing method of capturing an image of a subject while emitting light from two light-emitting sources toward the subject, the light-emitting sources being configured so that color temperatures of light emitted from the respective light-emitting sources are different from each other and a ratio between the volumes of light emitted from the light-emitting sources is variably controllable, the method comprising: a correcting step of correcting target values on the basis of at least two measured values related to the two light-emitting sources, the target values representing color information related to mixed color of light from the two light-emitting sources and being different from the measured value, the number of the target values being larger than the number of the measured values; a light-source color obtaining step of obtaining a light-source color of ambient light; a preliminary image capturing step including a no-light-emission image capturing step of capturing an image of the subject without light emission from the two light-emitting sources, and a light-emission image capturing step of capturing an image of the subject with light emitted from the two light-emitting sources; a light-emitting source light volume obtaining step of obtaining light volume information indicating a relationship between the light volume related to ambient light and the total volume of light from the two light-emitting sources, on the basis of the images of the subject captured in the preliminary image capturing step; an image capturing step of capturing an image of the subject while emitting light from the two light-emitting sources toward the subject in such a manner that the volumes of light emitted from the two light-emitting sources respectively correspond to those represented by a predetermined point which is (i) an intersection point of a first line and a line segment or (ii) a point close to the intersection point in xy chromaticity coordinates, on the basis of (a) the intersection point, (b) the light volume information obtained in the light-emitting source light volume obtaining step, and (c) corrected values of the target values representing color information, which are corrected in the correcting step, the first line passing through a first coordinate point in the xy chromaticity coordinates which represents the light-source color obtained in the light-source color obtaining step, the first line being drawn so as to cross the line segment at a predetermined angle, the line segment connecting two coordinate points in the xy chromaticity coordinates which points respectively represent colors of light emitted from the respective two light-emitting sources; and a White Balance adjustment step of performing White Balance adjustment on the image captured in the image capturing step on a basis of a White Balance adjustment correction value obtained with reference to a second coordinate point which is on a second line and corresponds to the light volume information obtained in the light-emitting source light volume obtaining step, the second line passing through the predetermined point and the first coordinate point in the xy chromaticity coordinates which represents to the light-source color.

4. The image capturing method according to claim 3 , wherein the correcting step includes a coordinate value correcting step of correcting coordinate values on the line segment in accordance with the two measured values on the basis of information stored in a storage unit in which the two measured values and the plurality of coordinate values are stored.

5. An image capturing method of capturing an image of a subject while emitting light from two light-emitting diodes toward the subject, the light-emitting diodes being configured so that color temperatures of light emitted from the respective light-emitting diodes are different from each other and a ratio between the volumes of light emitted from the light-emitting diodes is variably controllable, the method comprising: a light-source color obtaining step of obtaining a light-source color of ambient light; a preliminary image capturing step including a no-light-emission image capturing step of capturing an image of the subject without light emission from the two light-emitting diodes, and a light-emission image capturing step of capturing an image of the subject with light emitted from the two light-emitting diodes; a light-emitting source light volume obtaining step of obtaining light volume information indicating a relationship between a light volume related to ambient light and a total volume of light from the two light-emitting diodes, on the basis of the images of the subject captured in the preliminary image capturing step; an image capturing step of capturing an image of the subject while emitting light from the two light-emitting diodes toward the subject in such a manner that volumes of light emitted from the two light-emitting diodes respectively correspond to those represented by a predetermined point which is (i) an intersection point of a first line and a line segment or (ii) a point close to the intersection point in xy chromaticity coordinates, on the basis of the intersection point and the light volume information obtained in the light-emitting source light volume obtaining step, the first line passing through a first coordinate point in the xy chromaticity coordinates which represents the light-source color obtained in the light-source color obtaining step, the first line being drawn so as to cross the line segment at a predetermined angle, the line segment connecting two coordinate points in the xy chromaticity coordinates which points respectively represent colors of light emitted from the respective two light-emitting diodes; and a White Balance adjustment step of performing White Balance adjustment on the image captured in the image capturing step on a basis of a White Balance adjustment correction value obtained with reference to a second coordinate point which is on a second line and corresponds to the light volume information obtained in the light-emitting source light volume obtaining step, the second line passing through the predetermined point and the first coordinate point in the xy chromaticity coordinates which represents to the light-source color, wherein the light-emitting source light volume obtaining step comprises: a step of obtaining distance information D (m, n) in image signals obtained from the image captured in the preliminary image capturing step, on the basis of the image signals and in accordance with the below-described Equation 2: D (m, n)=(LV 0 −LOG 2 (Y 1 (m, n)/Y 0 (m, n)−1))/2, where: (m, n) represents a location in horizontal and vertical directions in the captured image; LV 0 represents a total volume of flash light from the two light-emitting diodes in APEX value; Y 0 (m,n) represents a brightness value at the location (m, n) obtained from the image captured in the no-light-emission image capturing step; Y 1 (m, n) represents a brightness value at the location (m, n) obtained from the image captured in the light-emission image capturing step; and LOG x represents a logarithm to the base x; a step of obtaining an area corresponding to a main subject from the captured image on the basis of the distance information D (m, n); and a step of obtaining the light volume information with respect to the area corresponding to the main subject.